Shared cell receiver for uplink capacity improvement in wireless communication networks

ABSTRACT

A wireless communication method and system are provided in which an uplink data stream that has uplink data associated with a user device is received. Channel performance data based at least in part on a portion of the uplink data stream is determined. A determination is made whether the channel performance data meets a predetermined performance level. The portion of the uplink data stream is discarded when the channel performance data does not meet the predetermined performance level. The portion of the uplink data stream is tagged for additional processing when the channel performance data meets the predetermined performance level.

TECHNICAL FIELD

The present invention relates to wireless communications, and inparticular to a receiver for a heterogeneous network.

BACKGROUND

The demand for wireless network access and performance has beenconstantly increasing due in part to the increased popularity ofwireless devices. Moreover, as wireless device functionality hasincreased, so has the quality and performance requirements for wirelessdata. For example, data intensive video streaming to a mobile devicetypically involves high quality service requirements such that the userexperience is not negatively affected. The result is that wireless datatraffic has been increasing almost exponentially while circuit switchedtraffic has been increasing at a slower pace. While protocols such aslong term evolution (LTE) provide higher bandwidth, there is a need tosupport an increasing number of devices which, in turn, have higherbandwidth requirements.

Wireless network operators have addressed the increased demand forwireless network access and performance in several ways. Some wirelessnetwork operators have deployed hierarchical cell structures such asthose found in heterogeneous network deployments in order to increasewireless access and performance. Heterogeneous network deployments areconfigured such that a macro cell coverage area includes one or morepico cells in which the mobile device communicates with the macro celland/or pico cell(s). For example, wireless network operators can placepico cells at “hot spots” to service specific areas within the macrocell coverage area that typically have a high number of mobile devices.

There are several configurations for heterogeneous deployments includinga multi-cell identification (ID) approach and a shared cell ID approach.The multi-cell ID approach includes assigning different cell IDs to eachmacro cell and pico cell such that each cell is required to transmitdifferent sync, broadcast and mobile device specific control channels.However, a dense deployment of pico cells within a macro cellsubstantially increases signaling due to frequency handovers for usersmoving at high speeds.

The shared cell ID approach to heterogeneous networks includes assigningthe same cell ID to the macro cell and each pico cell within a macrocell coverage area. The shared cell approach simplifies signaling fromthe mobile device perspective as the mobile device does not distinguishthe macro cell from the pico cell, i.e., the mobile device only “sees”one cell ID while traveling within the macro cell coverage area. Also,the need for additional control signaling overhead associated withhand-offs within the macro cell coverage region is avoided as the mobiledevice moves between pico cells. The shared cell ID approach also avoidsproliferation of cell IDs that occurs in the multi-cell ID approach.

However, the shared cell ID approach is not without faults. For example,a receiver at the macro cell may receive mobile device traffic forwardedfrom each pico cell. Processing the received traffic can require asubstantial amount of resources. For example, the receiver at a macrocell treats the shared cells as a distributed antenna system in whichall the link signals of UEs received from the pico cells are summedwithout regard to the properties of each uplink signal. While datavolume scales linearly with each additional uplink signal that is beingprocessed, processing for antenna combining requires a computationalcomplexity that grows exponentially with the number of antennas orreceived uplink signals. In other words, processing additional uplinksignals for antenna combining can rapidly become an issue for limitedcomputational resources. Also, processing all uplink signals receivedfrom the pico cells adds noise to the overall received signal, which inturn reduces data throughput. Therefore, current macro cell receiversare unable to take advantage of the different signal informationprovided by the shared cell approach.

SUMMARY

The present invention advantageously provides a device, system andmethod for enhancing capacity and performance of the shared cell.

According to one embodiment, a wireless communication system is providedfor use in a communication network. The system includes a network devicethat has a cellular identification (cell ID). The network deviceforwards an uplink data stream that has uplink data associated with auser device. A base station is in communication with the network device.The base station has the same cell ID as the cell ID of the networkdevice. The base station includes at least one receiver which receivesthe uplink data stream from the network device. The base stationincludes a processor configured to determine channel performance databased at least in part on a portion of uplink data stream. The processoris configured to determine whether the channel performance data meets apredetermined performance level and to discard the portion of the uplinkdata stream when the channel performance data does not meet thepredetermined performance level. The processor is configured to tag theportion of the uplink data stream for additional processing when thechannel performance data meets the predetermined performance level.

According to another embodiment, a wireless communication method isprovided in which an uplink data stream that has uplink data associatedwith a user device is received. Channel performance data based at leastin part on a portion of the uplink data stream is determined. Adetermination is made whether the channel performance data meets apredetermined performance level. The portion of the uplink data streamis discarded when the channel performance data does not meet thepredetermined performance level. The portion of the uplink data streamis tagged for additional processing when the channel performance datameets the predetermined performance level.

According to another embodiment, a wireless communication system isprovided that includes a network device that has a cellularidentification (cell ID). The network device forwards a data streamhaving uplink data associated with a user device. A base station incommunication with the network device in which the base station has thesame cell ID as the cell ID of the network device. The base stationincludes at least one receiver in which the at least one receiverreceives the first data stream. The base station includes a processor.The processor is configured to determine channel performance data basedat least in part on a portion of the data stream relayed from a userdevice to a base station. The processor is configured to determinehearability data in which the hearability data indicates whether thechannel performance meets a signal criteria. The processor is configuredto schedule resource blocks for the first user device based at least inpart on the first hearability data.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention, and theattendant advantages and features thereof, will be more readilyunderstood by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings wherein:

FIG. 1 is block diagram of a communication system using shared cellreceivers for receiving uplink data in accordance with the principles ofthe invention;

FIG. 2 is a block diagram of a plurality of shared cells constructed inaccordance with the principles of the invention;

FIG. 3 is a block diagram of an exemplary diagram of receiver processesin accordance with the principles of the invention;

FIG. 4 is flowchart of an exemplary forwarding process in accordancewith the principles of the invention;

FIG. 5 is a flowchart of an exemplary process for tagging uplink data inaccordance with the principles of the present invention;

FIG. 6 is a flowchart of another exemplary process for tagging uplinkdata in accordance with the principles of the present invention; and

FIG. 7 is a flowchart of an exemplary hearability process in accordancewith the principles of the present invention.

DETAILED DESCRIPTION

The present invention advantageously provides a device, system andmethod capable of improving performance of a macro cell. Accordingly,the system and method components have been represented where appropriateby conventional symbols in the drawings, showing only those specificdetails that are pertinent to understanding the embodiments of thepresent invention so as not to obscure the disclosure with details thatwill be readily apparent to those of ordinary skill in the art havingthe benefit of the description herein.

Referring now to the drawing figures, in which like referencedesignators refer to like elements, there is shown in FIG. 1 anexemplary communication system that improves performance of a macro cellin accordance with the principles of the present invention anddesignated generally as “10.” System 10 may include one or more userdevices 12 a to 12 n (collectively referred to as “user device 12”), oneor more reception/transmission nodes 14 a to 14 n (collectively referredto as “R/T node 14”), one or more nodes 16 a to 16 n (collectivelyreferred to as “node 16”), one or more packet cores 18 (collectivelyreferred to as “packet core 18”) and one or more networks 20 a to 20 n(collectively referred to as “network 20”).

User device 12 may include a transmitter, receiver, processor and memoryas is known in the art. User device 12 may communicate with R/T node 14and node 16 via a communications network using communication protocolsknown in the art, e.g., using Internet Protocols along with LTEstandards. User device 12 may communicate with R/T node 14 and node 16over one or more uplink (UL) channels and/or different UL paths using,for example, long term evolution (LTE) standards, e.g., uplink sharedchannel (UL-SCH) among other uplink channels known in the art. Forexample, uplink signals transmitted to node 16 by user device 12 may be“sniffed” by R/T nodes 14 as discussed in detail below with respect toFIG. 4. The communications network may include a wireless communicationsnetwork. User device 12 may include a mobile device, tablet, laptop,computer, personal digital assistant (PDAs), server, long term evolution(LTE) enabled device and the like.

R/T node 14 may include transmitter 22 and receiver 24 for communicatingat least with user device 12 and node 16 using communication protocolsknown in the art, e.g., using Internet Protocols along with LTEstandards. R/T node 14 may include one or more antennas forcommunicating with user device 12, e.g., main and diversity antennas.R/T node 14 may communicate with node 16 via a common public radiointerface (CPRI) line. The CPRI line may include a fiber opticcommunication link or other high-seed communication link. R/T node 14may be a remote radio unit (RRU).

R/T node 14 may include processor 26 such as a central processing unit(CPU) for performing node functions described herein. R/T node 14 mayinclude memory 28 that stores forwarding module 30, among other modules.In particular, memory 28 may include non-volatile and volatile memory.For example, non-volatile memory may include a hard drive, flash memory,memory stick and the like. Also, volatile memory may include randomaccess memory and others known in the art. Memory 28 may store programinstructions, which when executed, provide the functionality describedherein for forwarding module 30. For example, forwarding module 30includes instructions, which when executed by processor 26, causeprocessor 26 to perform the forwarding process, discussed in detailbelow with reference to FIG. 4. R/T node 14 may be a low power remoteradio unit providing functionality described herein.

Node 16 may include transmitter 32, receiver 34, processor 36 and memory38 in communication with each other. In particular, transmitter 32,receiver 34, processor 36 and memory 38 may generally correspond to thecomponents of R/T node 14, with size and performance being adjustedbased on design needs, while providing the functionality describedherein with respect to node 16. For example, transmitter 32 and receiver34 may provide transmission and reception of data communications to/fromuser device 12, R/T node 14 and packet core 18, among othercommunication devices and servers. For example, node 16 may receiveuplink channel signals associated with user device 12 directly from userdevice 12. Node 16 may also receive uplink channels signals from userdevice 12 via R/T node 14, i.e., R/T node 14 receives replicas ofinterference signals or uplink data streams that may be forwarded tonode 16 for further processing such as interference cancellation. Eachuplink data stream may include respective uplink data or channel signalsassociated with one or more user devices 12 that may be used forinterference estimation. The uplink channel signal may include uplinkshared channel (UL-SCH) among other uplink channels in accordance withLTE standards.

Memory 38 includes channel performance (CHP) tagging module 40, overlaptagging module 42, interference module 44 and hearability module 46,among other modules. CHP tagging module 40 tags uplink data received atnode 16. For example, CHP tagging module 40 includes programinstructions, which when executed by processor 36, cause processor 36 toperform the channel performance tagging process, discussed in detailbelow with respect to FIG. 5. Overlap tagging module 42 tags uplink datareceived at node 16. For example, overlap tagging module 42 includesprogram instructions, which when executed by processor 36, causesprocessor 36 to perform the overlap tagging process, discussed in detailbelow with respect to FIG. 6.

Interference module 44 includes program instructions, which whenexecuted by processor 36, cause processor 36 to perform multi-antennabased interference cancellation. The interference cancellation mayinclude maximum ratio combining (MRC), interference rejection combining(IRC), among other multi-beam interference cancellation techniques, asis well known in the art. Replicas of interference signals received fromR/T nodes 14 may be used as reference signals for performinginterference cancellation. Hearability module 46 includes programinstructions, which when executed by processor 36, cause processor 36 toperform the hearability process, discussed in detail below with respectto FIG. 7.

In one embodiment, node 16 is a central base station such as a centraleNodeB (CeNodeB) that provides a macro cell coverage area. R/T node 14may be a base station such as an eNodeB or remote radio unit (RRU) thatforwards uplink data received from user device 12 to node 16 asdescribed herein. R/T node 14 has a respective coverage area within themacro cell coverage area in which node 16 transmits signals at a higherpower than the R/T node 14, e.g., R/T node 14 is a pico cell. Node 16and R/T node 14 may be in a shared cell configuration such that bothnode 16 and R/T node 14 transmit the same cellular specific signalswithin the macro cell coverage area of node 16, e.g., coordinatedmulti-point (CoMP) transmission. R/T nodes 14 served by a specific node16 may have the same cell ID as the specific node 16, i.e., shared cellconfiguration.

Packet core 18 may be an Internet Protocol (IP) based core network. Forexample, packet core 18 may be an evolved packet core (EPC) network thatis based on end-to-end IP transmission in and out of the EPC network,e.g., all-IP based network. Data and voice may be communicated throughEPC via IP packets. Packet core 18 may include server gateways, packetdistribution network gateways and mobile management entities (notshown), among other servers and entities as is well known in the art.Network 20 may include communication networks such as wide areanetworks, local area networks and the like. Network 20 may providevarious voice and data related service, content and the like to userdevice 12 via packet core 18.

An exemplary shared cell configuration constructed in accordance withthe principles of the invention is described with reference to FIG. 2.Node 16 a has a coverage area that includes R/T node 14 a, 14 b, 14 cand 14 d. While four R/T nodes 14 are illustrated within the coveragearea of node 16 a, one of ordinary skill in the art at the art willunderstand that the invention is not limited to four R/T nodes 14. Othernumber of R/T nodes 14 may be implemented within the shared cellcoverage area of node 16 a. In particular, shared cell A may beconfigured in a heterogeneous configuration such that node 16 a and R/Tnodes 14 a, 14 b, 14 c and 14 d share the same cellular identification,i.e., LTE shared cell. As a result, user device 12 a is unable todistinguish between received transmission signals from R/T node 14 b andnode 16 a as the signals are associated with a single cell ID. R/T nodes14 a, 14 b, 14 c and 14 d may be connected to node 16 a via a CPRIcommunication link (not shown). Several exemplary transmission signalsfrom respective user devices 12 are indicated by arrows in whichreceived signal strength at node 16 and R/T node 14 is indicated by thelines of the arrows, i.e., solid arrows indicate greater received signalstrength than the received signal strength of the dashed arrows. Node 16b includes R/T node 14 e in which node 16 b and R/T node 14 e have thesame cell ID, i.e., shared cell B.

R/T node 14 b has a coverage area that includes user device 12 a. Forexample, user device 12 a may be physically located within R/T node 14 bcoverage area. R/T node 14 c has a coverage area that includes userdevice 12 b, e.g., hearability data indicates user device 12 a is withincommunication range of R/T node 14 b as discussed below with respect toFIG. 7. Devices 12 a and 12 b may communicate with R/T nodes 14 b and 14c, respectively, and node 16 a such that R/T node 14 b forwards signalsreceived from user device 12 a, i.e., provides “straight forwarding” asdiscussed below with respect to FIG. 4. Node 16 b defines a coveragearea located adjacent to node 16 a coverage area, i.e., adjacent sharedcell. Node 16 b may include one or more R/T nodes 14 such as R/T node 14e. R/T node 14 e is located within and at the edge of node 16 b coveragearea. Device 12 c is located within the coverage area defined by R/Tnode 14 e such that user device 12 c communicates with node 16 b and R/Tnode 14 e. Due to the proximity of user device 12 b to the edges of node16 a and 16 b coverage areas, user device 12 b transmission signals mayadditionally be received at R/T node 14 e located within node 16 bcoverage area and/or received at node 16 b. Also, user device 12 ctransmission signals may additionally be received at R/T node 14 clocated within node 16 a coverage area and/or at node 16 a such that R/Tnode 14 c “sniffs” signals from user device 12 c associated with sharedcell B, as discussed below with respect to FIG. 4.

Furthermore, one or more nodes 16 may be in communication with eachother such as to transfer data between each other. For example, node 16a and 16 b may communicate high interference indicator (HII) informationwith each other via a X2 communication link. HII information providesinformation to neighboring shared cells regarding resource blocks thathave been scheduled for use within a macro cell or node 16. For example,node 16 b may communicate HII information to node 16 a indicating thatresource blocks have been scheduled for transmission at R/T pointswithin shared cell B. By indicating scheduled resource blocks withinHII, node 16 a is able to determine resource blocks that provide usefulreplicas of interference signals that may be used for interferencecancellation, i.e., node 16 is able to determine overlapping resourceblocks based at least in part on the HII information.

An exemplary diagram of receiver processing for providing uplinkcapacity improvement is described with reference to FIG. 3. Receiverprocesses 48 include receiving a plurality of uplink data streams fromR/T nodes 14 a-14 n via respective communication links, i.e., receivesdesired UL signals, general interference signals, and replicas ofinterfering signals from one or more R/T nodes 14. Each communicationlink may have an associated delay 50 a-50 n (Δ_(a-n)) that maycompensated for such that the received uplink data streams aresynchronized, i.e., receiver processes 48 may include applying a timingoffset to each uplink data stream. Processing block 58 may include aFast Fourier transform (FFT) 52, pilot signal processing 54 and sharedchannel (SCH) processing 56 on the plurality of uplink data streams.Processing block 58 may be repeated for each R/T node 14. Also, highinterference indicators (HIIs) from one or more nodes 16 may be received60 and processed 62. After SCH processing 56 and HII processing 62, thefunctionality described herein with respect to tagging module 40 andinterference module 44 may be performed, i.e., includes per user device12 or user equipment (UE) and R/T SCH selection 64 and per UE signal tointerference-plus-noise ratio (SINR) optimization 66. Furthermore, afterpilot signal processing 54 but before SCH processing 56, thefunctionality described herein with respect to hearability module 46 maybe performed, i.e., UE hearability assessment 70. SCH processing 56 maybe performed in the first or second layers of processing.

Hearability data from the UE hearability assessment 70 process may beforwarded to the uplink (UL) scheduler for use in scheduling commonresources blocks as described with reference to FIG. 7. After the firstlayer of processing, the remainder of receiver processing 68 such as asecond layer of processing described herein may be performed. In otherwords, receiver processes 48 provide uplink capacity improvements viaone or more modules described herein by exploiting different conditionsat each R/T node 14 for each user device 12 while keeping the complexityof processing low.

It is contemplated that the receiver processes 48 can be performed byone or more of receiver 34 and/or processor 36, separately or incombination, and can be based on instantiation of one or more of modules40, 42, 44 and 46 as described above.

An exemplary process for forwarding uplink data is described withreference to FIG. 4. R/T node 14 determines whether an uplink datastream has been received, e.g., R/T node 14 receives uplink data streamsthat can be used by node 16 for interference estimation (Step S100). Forexample, processor 26 may determine that an uplink data streamassociated with user device 12 has been received. If no uplink datastream is determined to have been received, the determination of StepS100 may be repeated, i.e., R/T node 14 continues to determine whetheruplink data streams or channel signals have been received from userdevice 12 associated with the same or adjacent macro cell. If R/T node14 determines that an uplink data stream has been received, the uplinkdata stream may be forwarded to node 16 via a communications link suchas a CPRI communication link (Step S102). For example, uplink dataassociated with a first user device 12 received at a first R/T node 14within a first node 16 coverage area may be transmitted to first node 16via CPRI communication link for processing. Forwarding uplink signalsreceived from user device 12 in the same cell coverage area or sharedcell as the R/T node 14 that received with signal is referred to as“straight forwarding” as these signals were intended to be received byR/T node 14. Forwarding uplink signals or discernible replica signalstransmitted by user device 12 in an adjacent shared cell from the R/Tnode 14 that received the signal is referred to as “sniffing” as thediscernible replica signal was not intended for R/T node 14 but R/T node14 sniffed the signal for use in interference estimation.

An exemplary process for tagging uplink data associated with an uplinkdata stream is described with reference to FIG. 5. Node 16 determinesthat uplink data has been received from one or more R/T nodes 14 (StepS104). Node 16 may receive uplink data forwarded from each R/T node 14such as straight forwarded signals. The forwarded uplink data may bereceived by node 16 at different times due communication link delay suchas link delay caused by transmission path length and/or processingdelays, among other delays associated with data communications. Node 16may apply a respective timing offset to compensate for individual linkdelay caused between R/T node 14 and node 16 such that uplink datareceived from the plurality of R/T nodes are substantially time alignedwith each other.

A first layer of processing may be commenced on the received uplink data(Step S106). The first layer of processing may include preliminaryshared channel processing in which a Fast Fourier Transform (FFT) isapplied to uplink data received from each R/T node 14. The FFT isapplied to each uplink data stream received at node 16 and the pilotsignal associated with the physical uplink shared channel (PUSCH) foreach stream examined, e.g., first layer of processing does not processthe uplink data beyond pilot extraction and analysis. The first layer ofprocessing for each uplink data stream received from a respective R/Tnode 14 may be processed substantially in parallel. For example, the FFTis performed on each uplink data stream at substantially the same timedue in part to the timing offsets applied to one or more uplink streamsthat synchronize the uplink data streams.

Node 16 selects a portion of uplink data corresponding to a first R/Tnode 14 and a first user device 12, i.e., node 16 selects user devicefor investigation and selects a pilot signal associated with user device12 to examine (Step S108). Node 16 has knowledge of all the uplink dataand user devices 12 scheduled within the macro cell such that Node 16 isable to loop through each user device 12 of interest and each R/T pointof interest knowing a priori what data to consider or select. Processor36 determines channel performance characteristic(s) of the selecteduplink data, i.e., determined based on the selected pilot signal (StepS110). The channel performance characteristic may include SINR, powerlevel, among other characteristics associated with channel performance.

A determination is made as to whether the channel performancecharacteristic exceeds a quality threshold (Step S112). The qualitythreshold may be a predetermined value such as a predetermined signal tointerference-plus-noise ratio (SINR) value. For example, processor 36may determine that the SINR of the selected uplink data, i.e., selectedpilot or reference signal (SINR_(pilot)), associated with first userdevice 12 is greater than a minimum SINR value (SINR₁). The minimum SINRvalue indicates a minimum acceptable SINR level associated with uplinkdata that provides useful information for the second layer of processingwithout deteriorating the result of the second layer of processing. Forexample, the first R/T node 14 forwards a “noisy” signal, i.e., uplinkdata, to node 16 that will add a substantial amount of noise to the netreceived signal if used in the second layer of processing, i.e., reducesthroughput and reduces interference cancellation accuracy. As such,uplink data that does not meet the quality threshold is not used in thesecond layer of processing.

If the channel performance characteristic is determined to not exceedthe predetermined quality threshold, node 16 discards the selecteduplink data associated with the channel performance characteristic,i.e., discard the selected portion of the uplink data stream (StepS114). Discarding uplink data indicates the selected uplink data maydeteriorate the result of the second layer of processing, e.g., thereplica interference signals forwarded from R/T node 14 may deteriorateinterference cancellation. Also, discarding uplink data allows receiver34 to provide low latency processing by reducing the uplink data volume,after initial FFT processing, to a level that is comparable to areceiver for a standard LTE cell. Alternatively or in addition to node16 performing Steps S106-S114, R/T node 14 may perform the first layerof processing and discarding functions described with respect to StepsS106-S114 such that uplink data is discarded at R/T node 14 based atleast in part on channel performance characteristic(s).

If the selected uplink data is discarded, the determination of StepS118, discussed below, is performed. If the channel performancecharacteristic is determined to exceed the predetermined qualitythreshold, then the selected uplink data is tagged for furtherprocessing, i.e., the selected portion of the uplink data stream istagged for use during the second layer of processing (Step S116).Tagging the selected uplink data may indicate that the uplink dataprovides useful information that increases the accuracy of the secondlayer of processing, e.g., the tagged uplink data provides usefulreplicas of interference signals that increase the accuracy ofinterference cancellation.

Node 16 determines whether additional uplink data has not been examined(Step S118). For example, processor 36 determines whether uplink datacorresponding to user device 12 under investigation has been receivedfrom another R/T node 14, i.e., several R/T nodes 14 may receive andforward uplink data transmitted from user device 12 under investigationby node 16. User device 12 may be within range of two or more R/T nodes14 in which the R/T nodes 14 will each forward uplink data received fromuser device 12. As such, receiver 34 may receive uplink datacorresponding to user device 12 that is received at plurality of R/Tnodes 14.

If the determination is made that uplink data received from another R/Tnode 14 corresponds to user device 12 under investigation, thecorresponding uplink data is selected (Step S120). Specifically, theportion of uplink data corresponding to user device 12 from another R/Tnode 14 is selected such that Step S110 is repeated with the newlyselected portion of uplink data, e.g., channel performancecharacteristic(s) are determined. If the determination is made thatuplink data from another R/T node 14 does not correspond to specificuser device 12, processor 36 processes the tagged uplink data, i.e., thetagged uplink data goes through a second layer of processing (StepS122). The tagged uplink data represents a replica of one or moreinterference signals that can be used in the second layer of processing.The second layer of processing may include multi-antenna processing thatis performed based at least in part on tagged uplink data correspondingto user device 12. In particular, interference cancellation may beperformed on an uplink data stream received directly from user device 12using the tagged uplink data as reference interference signals. Thereference interference signals improve the performance of interferencecancellation, thereby increasing data throughput. The multi-antennaprocessing may include maximum ratio combining (MRC), interferencerejection combining (IRC), among other multi-antenna or multi-beamprocessing techniques.

The first and second layers of processing performed on the uplink dataallow the system to provide increased performance and uplink channelcapacity while keeping the processing complexity at receiver 34 to aminimum. For example, specific user device 12 may transmit uplink datathat is received at four R/T nodes 14 in which node 16 receives fourindividual uplink data streams each having uplink data associated withspecific user device 12. Out of the four streams of uplink data, onlytwo streams may have a signal quality sufficient to pass the first layerof processing, i.e., SINR_(pilot) is greater than SINR₁. Therefore, twoof the streams will be discarded. The first level of processing providessignificant data volume reduction by discarding uplink data not meetingthe quality threshold. The first level of processing also provides SINRimprovements by preventing low SINR signals from being included in thesecond layer of processing, i.e., low SINR signals may reduce theoverall SINR of the uplink data to be processed via the second layer ofprocessing. The first layer of processing may be performed by R/T nodes14 and/or node 16. For example, the first layer of processing may beperformed at one or more R/T nodes 14 such that one or more streams ofuplink data are discarded by the R/T nodes 14, i.e., are not forwardedto node 16, such that backhaul capacity requirements are reduced.

Moreover, the second layer of processing provides interferencecancellation based on tagged uplink data. Performing interferencecancellation using tagged uplink data and not discarded uplink dataincreases the performance of the interference cancellation. Discardinguplink data reduces the processing complexity at node 16 while stillproviding improved performance because the amount of uplink data streamsto be processed by the second layer of processing is reduced such thatthe processing complexity of multi-beam processing is reduced.

Once all of the uplink data or returns from a given user device 12 havebeen considered and processed across all R/T nodes 14 in the macro cell,a determination is made as to whether there are other user devices 12within this macro cell that have uplink data scheduled in the subframe,e.g., whether a different device with scheduled uplink data has yet tobe investigated by node 16 (Step S124). If it is determined that adifferent user device 12 has associated uplink data across R/T nodes 14within node 16, the portion of the uplink data stream, i.e., PRBs, areselected for investigation (Step S126), and the process of tagging datafor the different user device across R/T nodes 14 is repeated for thenewly selected PRBs.

An exemplary process for tagging overlapping uplink data is describedwith reference to FIG. 6. Processor 36 determines that uplink data hasbeen received from a plurality of R/T nodes 14 (Step S128). For example,processor 36 determines receiver 34 has received individual uplink datastreams or sniffed signals from a plurality of R/T nodes 14. Node 16selects physical resource blocks (PRBs) corresponding to one of theplurality of R/T nodes 14 (Step S130). An individual uplink data streamfrom R/T node 14 may contain a plurality of PRBs in which one set ofPRBs is selected for processing. A channel performance characteristic(s)corresponding to the selected PRBs is determined (Step S132). Forexample, the channel performance characteristic may include SINR(SINR_(PRB)), power level, among other characteristics associated withchannel performance. A determination is made whether the channelperformance characteristic meets a predetermined channel performancelevel, e.g., whether SINR_(PRB) is less than a predetermined performancelevel (SINR₂) (Step S134). The required performance level should be metto provide an accurate reference to estimate the interference signal,i.e., SINR_(PRB)<SINR₂.

If the determination is made that the channel performance characteristicis less than the predetermined performance level, a determination ismade as to whether a signal power characteristic is greater than apredetermined power threshold, i.e., whether a second channelperformance characteristic is greater than a second performance level(Step S136). For example, node 16 determines whether the power levelassociated with the selected PRBs is greater than the predeterminedpower threshold, i.e., P_(PRB) greater than P_(threshold). Thepredetermined power threshold may indicate a minimum power needed toprovide an interference reference signal that will not reduce theaccuracy of interference cancellation.

If the determination is made that the signal power characteristic isgreater than a predetermined power threshold, a determination is made asto whether the selected PRBs overlap with other PRBs scheduled for useby another user device 12 at another R/T node 14 served by a differentnode 16 (Step S138). For example, PRBs corresponding to first userdevice 12 communicating with first R/T node 14 served by first Node 16may overlap with PRBs corresponding to another user device 12 incommunication with another R/T node 14 served by a different node 16,i.e., served by a different macro cell. The overlap corresponds to userdevices in different macro cells, i.e., node 16 a and node 16 b. Theoverlap determination of Step S138 may be based at least in part on HIIinformation received from adjacent macro cells, i.e., HII informationindicates PRBs scheduled at adjacent node 16.

If the determination is made that the PRBs do not overlap, the selectedPRBs are discarded (Step S140). Discarding PRBs indicates that thecharacteristics of the selected PRBs do not provide useful interferencereference signals for interference cancellation, i.e., the selected PRBsmay add noise and/or reduce accuracy. After discarding the selectedPRBs, a determination is made as to whether there are any PRBs that havenot been examined (Step S144). For example, the uplink data associatedwith a specific R/T node 14 may include a plurality of PRBs, each ofwhich are selected for processing.

If the determination is made that PRBs have not been examined, node 16selects another set of PRBs (Step S146). The selected PRBs are processedas discussed above with respect to Step S132. If the determination ismade that all PRBs associated with an uplink data stream from specificR/T node 14 have been examined, a determination is made as to whetherPRBs associated with another R/T node 14 has not be examined (StepS148). If node 16 determines that uplink data associated with anotherR/T node 14 have not been examined, PRBs associated with the unexamineduplink data are selected, i.e., processor 36 selects uplink dataassociated with another R/T node 14 (Step S150). The selected PRBs areprocessed as discussed above with respect Step S132.

Referring back to Step S138, if the determination is made that theselected PRBs overlap with other PRBs in use by another user device 12at a different R/T node 14 service by a different macro cell, theselected PRBs are tagged for further processing (Step S142). Forexample, tagging PRBs indicates that the tagged PRBs may provide usefulinterference reference signals for use in the second layer ofprocessing. After tagging PRBs, the determination of Step S144 may berepeated. Referring back to Step S148, if the determination is made thatall PRBs associated with received uplink data have been examined acrossall R/T nodes 14 within a given node 16 or macro cell, the tagged PRBsare provided to the interference processor 44 of node 16 for that macrocell. For example, interference cancellation is performed based at leastin part on the tagged PRBs available through the R/T nodes' sniffedsignals or receipt of UL signals from user devices 12 in adjacent macrocells. The tagged PRBs represent a replica of one or more interferingsignals forwarded from R/T node 14 within the macro cell that may beused for the second layer of processing, e.g., interferencecancellation.

An exemplary process for scheduling RBs is described with reference toFIG. 7. In particular, node 16 determines whether at least two userdevices 12 have complimentary hearability across at least two R/T nodes14. Node 16 determines uplink data has been received from R/T nodes 14,e.g., receives straight forwarded signals (Step S154). For example,processor 36 determines uplink data has been received from respectiveR/T nodes 14 via a CPRI communication link. Node 16 selects first userdevice 12 having associated uplink data for processing (Step S156).

Uplink data received from each R/T node 14 that is associated with firstuser device 12 is selected (Step S158). For example, the pilot signal orreference signal of any of the uplink channels such as shared channel(SCH), physical uplink control channel (PUCCH), sounding referencesignal (SRS) and random access channel (RACH), among other uplinkchannels according to LTE standards may be selected for processing. Theterms “first” and “second” are used herein to indicate a specific userdevice 12 and/or R/T node 14. An uplink performance characteristicassociated with the selected uplink data is determined (Step S160). Theuplink performance characteristic may include SINR, power level, amongother signal characteristics associated with channel performance. Thechannel performance characteristics of each individual uplink datastream associated with first user device 12 is determined. For example,the uplink performance characteristics of a first uplink data streamfrom R/T node 14 and a second uplink data stream from another R/T node14 are determined in which both first and second uplink data streams areassociated with first user device 12.

The weighted sum of channel performance characteristics is determined(Step S162). The weighted sum of channel performance characteristicsindicates the SINR contribution associated with first user device 12 forone or more uplink channels such SCH, PUCCH, SRS and RACH, among otheruplinks channels in accordance with LTE standards. Hearability data isdetermined (Step S164). In particular, hearability data may bedetermined based at least in part on the weighted sum of channelperformance characteristics associated with first user device 12. Forexample, the weighted sum of SINR values may be filtered based on amemory time constant to generate filter values in which the filtervalues are compared to predetermined hearability thresholds to determinewhether the first user device 12 is “within” or “outside” thecommunication range of R/T node 14.

In other words, hearability data indicates whether first user device 12is within the communication range or outside the communication range ofa specific R/T node 14, i.e., indicates whether a signal received at R/Tnode 14 from specific user device 12 meets a predetermined signalquality indicating user device 12 is within or outside the communicationrange of R/T node 14. The weighted sum of channel performancecharacteristics may be averaged over several radio subframes to increaseaccuracy and reliability of the weighted sum in which a memory constantmay be used to weigh the most recent measurements as being morevaluable. If no uplink data is associated with user device 12 during oneof the iteration of determining the weighed SINR contribution, i.e., nouplink channel is present for first user device 12, node 16 mayinterpolate between the last SINR contribution and the next SINRcontribution to determine the missing SINR contribution.

A determination is made as to whether the uplink data corresponds to adifferent user device 12, i.e., whether additional uplink data needs tobe examined (Step S166). If the determination is made that uplink datacorresponds to a different user device 12, the uplink data correspondingto the different user device 12 is selected, i.e., a portion of theuplink data stream is selected (Step S168). The processing of Step S160,as discussed above, is performed for the selected uplink data. If thedetermination is made that the uplink data does not correspond to adifferent user device 12, hearability data may be forwarded to an uplinkscheduler such that the uplink scheduler schedules resource blocks basedat least in part on the hearability data. Resource blocks can bescheduled based on the determined hearability data such that differentuser devices 12 communicating with respective R/T nodes 14 within a node16 or macro cell coverage area are scheduled distinct or common resourceblocks.

For example, hearability data associated with first user device 12 mayindicate that the first user device 12 is not hearable or within thecommunication range at first R/T node 14 but is hearable at second R/Tnode 14. The coverage area of the second R/T node, e.g., pico cell,includes first user device 12 while first R/T node 14 coverage area doesnot include first device, i.e., the received signal from first userdevice 12 at first R/T node 14 is too deteriorated or weak. Thehearability data associated with a second user device 12 may indicatethat second user device 12 is hearable at first R/T node 14 but nothearable at second R/T node 14. In other words, the coverage area offirst R/T node, i.e., pico cell, includes second user device 12 whilethe coverage area of second R/T node 14 does not include second device14, i.e., the received signal from second user device 12 at second R/Tnode 14 is too deteriorated or weak.

Based on the hearability data, the uplink scheduler may scheduleresources common with both first user devices 12 and second user device12, i.e., schedules on common resource blocks (RBs) to different userdevices 12 served by the same macro cell or node 16. Referring to FIG.2, user device 12 a and user device 12 b may be scheduled commonresource blocks based at least in part on determined hearability data,i.e., the scheduler may assign PRBs that can be re-used between userdevices 12 a and 12 b across R/T nodes 14 served by node 16 a. First andsecond user devices 12 may use common resources that do notsubstantially interfere with each other. Scheduling at least two userdevices 12 on common or corresponding resources within a macro cellincreases the amount of user devices 12 that can serviced within a macrocell while positively impacting aggregate data throughput.

Moreover, node 16 may provide the same downlink signals to all R/T nodes14 such that complementary user devices 12 must be scheduled on distinctdownlink channels. The uplink hybrid automatic repeat request (HARQ) onthe physical HARQ indicator channel (PHICH) may be distinguished betweencomplementary user devices 12. For example, the different referencesignals phase rotations may be specified in the uplink grant.Alternatively, the complementary user devices 12 may be scheduleddifferent physical uplink shared channel (PUSCH) PRB start points.

The present invention can be realized in hardware, software, or acombination of hardware and software. Any kind of computing system, orother apparatus adapted for carrying out the methods described herein,is suited to perform the functions described herein.

A typical combination of hardware and software could be a specialized orgeneral purpose computer system having one or more processing elementsand a computer program stored on a storage medium that, when loaded andexecuted, controls the computer system such that it carries out themethods described herein. The present invention can also be embedded ina computer program product, which comprises all the features enablingthe implementation of the methods described herein, and which, whenloaded in a computing system is able to carry out these methods. Storagemedium refers to any volatile or non-volatile storage device.

Computer program or application in the present context means anyexpression, in any language, code or notation, of a set of instructionsintended to cause a system having an information processing capabilityto perform a particular function either directly or after either or bothof the following a) conversion to another language, code or notation; b)reproduction in a different material form.

It will be appreciated by persons skilled in the art that the presentinvention is not limited to what has been particularly shown anddescribed herein above. In addition, unless mention was made above tothe contrary, it should be noted that all of the accompanying drawingsare not to scale. A variety of modifications and variations are possiblein light of the above teachings without departing from the scope andspirit of the invention, which is limited only by the following claims.

What is claimed is:
 1. A wireless communication system, comprising: afirst network device having a cellular identification, cell ID, thefirst network device forwarding a first uplink data stream having firstuplink data associated with a user device; and a base station incommunication with the first network device, the base station having thesame cell ID as the cell ID of the first network device, the basestation including: at least one receiver, the at least one receiverreceiving the first uplink data stream from the first network device;and a processor, the processor configured to: determine channelperformance data based at least in part on a portion of first uplinkdata stream; determine whether the channel performance data meets apredetermined performance level; discard the portion of the first uplinkdata stream when the channel performance data does not meet thepredetermined performance level; and tag the portion of the first uplinkdata stream for additional processing when the channel performance datameets the predetermined performance level.
 2. The system of claim 1,wherein the additional processing includes performing interferencecancellation based at least in part on the tagged portion of the firstuplink data stream.
 3. The system of claim 2, wherein the portion offirst uplink data stream is a reference signal in an uplink sharedchannel, UL-SCH.
 4. The system of claim 2, further comprising a secondnetwork device, the second network device forwarding a second uplinkdata stream having the first uplink data associated with the userdevice, the second network device having the same cell ID as the basestation, the at least one receiver receiving the second uplink datastream; and the base station processor further configured to: determinesecond channel performance data based at least in part on a portion ofsecond uplink data stream; determine whether the second channelperformance data meets the predetermined performance level; disregardthe portion of the second uplink data stream when the second channelperformance data does not meet the predetermined performance level; andtag the portion of the second uplink data stream for the additionalprocessing when the second channel performance data meets thepredetermined performance level, the interference cancellation is basedat least in part on the tagged portion of the second uplink data stream.5. The system of claim 2, wherein the first uplink data stream includessecond uplink data associated with a second user device, the second userdevice being associated with a second base station having a differentcell ID than the cell ID of the first base station; and the interferencecancellation is based at least in part on a portion of the second uplinkdata stream.
 6. The system of claim 5, wherein the portion of the firstuplink data stream is a physical resource block, PRB.
 7. The system ofclaim 6, wherein the predetermined performance level includes a maximumsignal to interference plus noise ratio, SINR, and minimum power level.8. The system of claim 6, wherein the PRB overlaps with another PRBscheduled for use by another user device associated with the second basestation.
 9. A wireless communication method, comprising: receiving afirst uplink data stream having uplink data associated with a userdevice; determining channel performance data based at least in part on aportion of the first uplink data stream; determining whether the channelperformance data meets a predetermined performance level; discarding theportion of the first uplink data stream when the channel performancedata does not meet the predetermined performance level; and tagging theportion of the first uplink data stream for additional processing whenthe channel performance data meets the predetermined performance level.10. The method of claim 9, wherein the additional processing includesperforming interference cancellation based at least in part on thetagged portion of the first uplink data stream.
 11. The method of claim10, wherein the portion of the first uplink data stream is a referencesignal in an uplink shared channel, UL-SCH.
 12. The method of claim 10,further comprising: receiving a second uplink data stream having theuplink data associated with the user device; determining second channelperformance data based at least in part on a portion of the seconduplink data stream; determining whether the second channel performancedata meets the predetermined performance level; discarding the portionof the second uplink data stream when the second channel performancedata does not meet the predetermined performance level; tagging theportion of the received second uplink data stream for additionalprocessing when the second channel performance data meets thepredetermined performance level; and the interference cancellation beingbased at least in part on the tagged portion of the second uplink datastream.
 13. The method of claim 10, wherein the user device isassociated with a first base station having a cell ID; and the methodfurther comprising receiving a second uplink data stream associated witha second user device, the second user device being associated with asecond base station having a different cell ID than the cell ID of thefirst base station; and the interference cancellation is based at leastin part on a portion of the second uplink data stream.
 14. The method ofclaim 13, wherein the portion of the first uplink data stream is aphysical resource block, PRB.
 15. The method of claim 14, wherein thePRB overlaps with another PRB scheduled for use by another user deviceassociated with the second base station.
 16. The method of claim 13,wherein the predetermined performance level includes a maximum signal tointerference plus noise ratio, SINR, and minimum power level.
 17. Awireless communication system, the system comprising: a first networkdevice having a cellular identification, cell ID, the first networkdevice forwarding a first data stream having uplink data associated witha first user device; a base station in communication with the firstnetwork device, the base station having the same cell ID as the cell IDof the first network device, the base station including: at least onereceiver, the at least one receiver receiving the first data stream; aprocessor, the processor configured to: determine first channelperformance data based at least in part on a portion of the first datastream relayed from a user device to the base station; determine firsthearability data, the first hearability data indicating whether thefirst channel performance meets a signal criteria; the first hearabilitydata being determined based at least in part on a weighted sum of firstchannel performance data associated with the first user device andschedule resource blocks for the first user device based at least inpart on the first hearability data.
 18. The system of claim 17, furthercomprising a second network device, the second network device forwardinga second data stream having uplink data associated with a second userdevice; the at least one receiver receiving the second data stream; theprocessor is further configured to: determine second channel performancedata based at least in part on a portion of the second data stream;determine second hearability data, the second hearability dataindicating whether the second channel performance meets the signalcriteria, the scheduling of the resource blocks includes scheduling thesecond user device based at least in part on the first and secondhearability data.
 19. The system of claim 18, wherein the first userdevice and second user device are scheduled on common resource blocks.20. The system of claim 18, wherein the second network device has thesame cell ID as the cell ID of the base station.